The 14-Day Pouch Problem
At a Canterbury secondary school, a Year 13 student has a brief to make 30 insulated lunch pouches for a kōhanga reo. The kōhanga needs packed lunches to stay below 8°C for four hours on a February day (ambient 26°C). The student's specifications are: unit cost no more than NZ$18, at least 60% recycled content by mass, and delivery in seven weeks. Prototype 2 uses 6 mm closed-cell polyethylene foam, a recycled PET shell, and a 200 g ice pack. In a test at 26°C, the internal temperature reaches 11.2°C after four hours. The zipper slider pulls off at 1,200 cycles; the brief requires 5,000 cycles. The only recycled-content zipper with a 5,000-cycle rating has a six-week lead time. A local virgin-nylon zipper costs $2.10 more per unit and arrives in two weeks. The kōhanga also asks for its logo printed on every pouch, which adds $1.80 per unit and four days.
1. Recommend what the student should do about the zipper and the thermal failure. Justify the trade-offs against the brief's specifications and the seven-week delivery date.
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The pouch fails two specifications at once: thermal performance (11.2°C against an 8°C limit) and zipper durability (1,200 cycles against 5,000). The fixes compete for the same $18 unit cost and the same seven-week window, so the student should treat this as a trade-off decision, not two isolated fixes.
Zipper: The six-week recycled zip leaves only one week to build and deliver 30 pouches, which is too risky. The local virgin-nylon zipper arrives in two weeks and is rated for the required cycles, so it is the lower-risk choice. The recycled-content specification is by mass; a zipper is a small fraction of the pouch, so switching should not push the pouch below 60% recycled content - but the student must calculate this, not assume it. Record the substitution in the brief with a reason.
Thermal: Adding a reflective foil layer and increasing the ice pack from 200 g to 300 g is likely to gain the 3.2°C needed, but it adds cost and mass. The student should test a revised prototype at 26°C with a real lunch, not just a temperature probe. If the cost then exceeds $18, the logo printing is the obvious item to defer because it is not a function-critical specification.
Decision: Use the local zipper, revise the insulation, run one more thermal test, and keep a week of contingency. This meets the hard specifications and the deadline; the alternative meets the recycled-zip preference but risks delivering nothing.
2. The kōhanga asks for the logo. Explain how the student should handle this request so that the brief stays coherent and the pouches still meet the kōhanga's needs.
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The logo request is a stakeholder need, but it is not in the agreed brief, so the student should not simply add it. Adding $1.80 per unit is $54 across 30 pouches and four days, which may push the unit cost over $18 and eat the contingency. The correct process is to evaluate the request against the brief, present the trade-off to the kōhanga, and agree a change if it is worth it.
Options:
- Printed logo: highest visual quality, but highest cost and lead time.
- Woven label sewn into the seam: likely under $0.60 per unit and can be done during assembly; durable through washing.
- Heat-transfer or stamp: cheap, but may crack or fade.
- Removable card: cheapest, but easily lost and not part of the product.
The student should recommend the woven label as the best fit: it satisfies the kōhanga's identity need, adds little cost, and does not compromise the thermal or zipper specifications. If the kōhanga insists on printing, the student should ask them to fund the difference or reduce another cost. The key is to document the change in the brief, with the reason and the agreement, so it is managed stakeholder consultation rather than scope creep. The student should also check that the label does not create a leak path or a washing problem.
3. Describe the evidence the student should collect in the final evaluation to show the pouches are fit for purpose for the kōhanga, and explain why each piece matters.
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Fitness for purpose means the pouch works for the kōhanga's actual use, not just that it passed a lab test. The student should collect evidence against each specification and against the wider brief.
- Thermal performance: at least three trials at 26°C with a realistic lunch and ice pack, using a data logger, including one trial where the pouch is opened at lunchtime. This matters because a single lab result at 11.2°C does not show the effect of opening, packing density, or a hot day.
- Zipper durability: a 5,000-cycle test or the supplier's certified rating, plus a pull test. This matters because the zipper was the earlier failure mode and children will open and close the pouch repeatedly.
- User trial: ask kaiako and tamariki to pack, open, close, wipe and label the pouches for a week. Record what they found. This matters because usability and independence are part of fitness for purpose.
- Wash and material durability: at least five wash cycles, check seams and recycled content calculation. This matters because food pouches get dirty and the recycled-content claim must be verified.
- Cost and delivery records: actual unit cost against $18 and delivery against the seven-week date. This matters because the brief is a package of constraints, not just a product.
The evaluation should also state what did not work and what the student would change, so the evidence supports a judgement rather than a description.